Leptin is a product of the Ob gene (Zhang et al., 1995 Nature 372:425-432). In its absence, mice develop extreme obesity resembling morbid obesity of humans. They also develop diabetes resembling human type II diabetes (Zhang et al., supra), and become infertile (Chehab et al., 1996 Nature Genetics 12:318-320). Restoration of leptin reverses these pathologies.
Currently, the only manner in which preparations of recombinant leptin can be assayed is by injection of large quantities into ob/ob mice (Campfield, 1995 Science 269:546-549; Rentsch 1995, Biochem Biophys Res Comm 214:131-136). Leptin activity is assessed based upon depression of feed intake and is highly variable among individuals. No mutually agreed upon standard of leptin activity exists. Therefore, a rapid, accurate assay for leptin bioactivity which utilizes small amounts of leptin would be desirable.